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"Dioxin Science Wars" Heat Up

"The latest skirmish in the decades-long scientific battle over the health risks of the most toxic form of dioxin is heating up. The Environmental Protection Agency fired the first shot of this new clash in May, when it issued a draft report classifying 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) as a known human carcinogen. EPA also for the first time set a safe daily dose for TCDD based on its adverse effects on reproduction.

Once finalized, EPA’s conclusions on TCDD will have wide-ranging repercussions. They will affect the extent—and thus the cost—of cleanups of areas contaminated with TCDD or related polycyclic aromatic hydrocarbons, including polychlorinated dibenzodioxins other than TCDD, polychlorinated dibenzofurans, and polychlorinated biphenyls (PCBs).

Some chemical manufacturers that are major producers and users of chlorine face liability for cleanup of sites contaminated with these compounds. They are readying retorts to the draft that target its scientific basis. The Pentagon is doing likewise because it too faces cleanup liabilities from its past use of PCBs."